Electronic testing systems are commonly used to measure or identify one or more analytes in a sample. Such testing systems can be used to evaluate medical samples for diagnostic purposes and to test various non-medical samples. For example, medical diagnostic meters can provide information regarding the presence, amount, or concentration of various analytes in human or animal body fluids. In addition, diagnostic test meters can be used to monitor analytes or chemical parameters in non-medical samples such as water, soil, sewage, sand, air, beverage and food products or any other suitable sample.
Diagnostic testing systems typically include both test media, such as diagnostic test strips, and a test meter configured for use with the test media. Suitable test media may include a combination of electrical, chemical, and/or optical components configured to provide a response indicative of the presence or concentration of an analyte to be measured. For example, some glucose test strips include electrochemical components, such as glucose specific enzymes, buffers, and one or more electrodes. The glucose specific enzymes may react with glucose in a sample, thereby producing an electrical signal that can be measured with the one or more electrodes. The test meter can then convert the electrical signal into a glucose test result.
There is a demand for improved test media. For example, in the blood glucose testing market, consumers consistently insist on test media that require smaller sample sizes, thereby minimizing the amount of blood needed for frequent testing. Consumers also demand robust performance and accurate results, and will not tolerate erroneous tests due to inadequate sample size. In addition, in all diagnostic testing markets, consumers prefer faster, cheaper, more durable, and more reliable testing systems.
Current methods of manufacturing diagnostic test media have inherent limits. For example, current methods for producing test media electrodes and depositing enzymes or other chemicals may have limited spatial resolution and/or production speeds. Furthermore, some production processes cannot be used to deposit some enzymes, chemicals, and electrodes. In addition, some production processes may be used to produce or deposit some test media components, such as electrodes or enzymes, while being incompatible with other components. Therefore, some test media production processes may require multiple production techniques, thereby increasing production cost and time, and decreasing product throughput.
Several methods for manufacturing biosensors have been proposed. One such method is described in U.S. Pat. No. 6,875,327 to Miyazaki et al. Miyazaki et al. describe a biosensor manufacturing process whereby a conductive layer is formed on a support. Electrodes are formed using a laser to form multiple “slits” in the conductive layer, which form electrical separations between the working, counter and detecting electrodes. Following electrode formation, chemical reagents are selectively applied to the conductive layer.
U.S. Pat. No. 6,805,780 to Ryu et al. describes a method for producing electrochemical biosensor test strips. The process includes forming a groove in a first insulating substrate and sputtering a metal onto the insulating substrate with the aid of a shadow mask to form a pair of electrodes. The shadow mask should be in close contact with the substrate to avoid deposited material entering gaps and reducing the quality of the pattern formed. The shadow mask may be placed in contact with a substrate, or may be formed by cutting a pattern in a plastic layer adhered to the substrate, which is termed “adhesive-type shadow mask.”
U.S. Published Application No. 2005/0161826 to Shah et al. describes a manufacturing method that utilizes shadow mask techniques and lift-off lithography. Lift-off lithography uses a photo-resist layer patterned to form a negative image of the conducting elements. A thin metal film is formed over the substrate by, for example, sputtering. Next, the photo-resist layer is removed by chemical stripping, leaving conductive elements formed by the metal that remains on the substrate. The shadow mask process is also used to form sacrificial structures on the substrate, and multiple layers of dielectric and conductor material may be formed using both processes. Initially a dielectric substrate base is formed, followed by patterning a blanket layer of conductive thin-film. Sacrificial structures may then be formed, using, shadow mask deposition. At least one dielectric layer is deposited on the multilayer circuit. Conductors and sacrificial structures may then be created and removed, forming multiple conductive and dielectric layers.
There exists the need to mass-produce biosensors cost effectively and with high precision. The prior art references have several limitations solved by the current invention. Although the electrode design described by Miyazaki et al. can provide a functional biosensor, improved methods of manufacturing biosensor electrodes are desirable. Specifically, other manufacturing methods may be used to lower the cost and/or increase the quality of electrode formation and biosensor performance. For example, steps described by Rye et al. may require the formation of a groove in the substrate, adding cost and complexity to biosensor manufacturing. Further, Rye et al. discloses the formation of a single test strip containing only two electrodes. Other limitations of the prior art include the fact that Shah et al. requires the application of at least one dielectric layer to form the multilayer circuit structure.
Accordingly, there is a need for improved methods of manufacturing diagnostic testing systems.